The Best Open-Source Invoicing Software in 2026
If you want invoicing software you can read the source of, self-host, and never get locked out of, open-source is the way to go. This is an honest rundown of the best open-source invoicing tools in 2026 — what each is good at, and how heavy it is to run.
What “open source” should actually get you
Not all “free” tools are open-source, and not all open-source tools are easy to self-host. The ones worth your time give you:
- Real ownership — your data lives where you put it, exportable anytime.
- A license you can trust — MIT or similar, no rug-pulls.
- A sane footprint — it shouldn’t take a server team to run an invoice tool.
The shortlist
| Tool | License | Self-host footprint | Hosted option | Best for |
|---|---|---|---|---|
| Inkvoice | MIT | One container, ~50–100 MB, SQLite | Yes | Owning your data + staying lightweight |
| Invoice Ninja | Elastic | PHP + MySQL, heavier | Yes | Power users who want every feature |
| InvoicePlane | MIT | PHP + MySQL | No | Dead-simple, no tiers |
| Crater | AAL | PHP + MySQL, mobile app | No | Freelancers who want a clean UI |
| Akaunting | GPL | PHP + MySQL | Yes (paid apps) | Full accounting, not just invoices |
Inkvoice
Free and MIT-licensed, built to stay light and modern (Bun + Hono + React). One ~50–100 MB container with native SQLite, so it runs on the cheapest VPS and deploys in minutes on Docker, Dokploy or Coolify. You get the get-paid-faster toolkit — read receipts, recurring invoices, quotes, statements — plus online card payments (Stripe & PayPal), multi-currency, 5 languages, and polished PDF templates. There’s a managed Cloud if you’d rather not self-host.
Invoice Ninja
The most feature-rich open-source option: tons of payment gateways, deep customization, time tracking. That power comes with a heavier PHP/MySQL stack and more setup.
InvoicePlane
Refreshingly simple and completely free with no paid tiers — great if you want plain invoicing and nothing else. Quieter development and a more dated stack.
Crater
A clean, modern UI with a companion mobile app, aimed at freelancers. Self-host only (no official hosted plan), on a PHP/MySQL stack.
Akaunting
More of a full accounting suite than an invoicing app — powerful if you need books, overkill if you just want to bill clients (and several features live behind paid apps).
How to choose
- Want lightweight + own your data + an optional hosted escape hatch? → Inkvoice.
- Need every advanced feature and don’t mind the weight? → Invoice Ninja.
- Want the absolute simplest free option? → InvoicePlane.
Try the Inkvoice live demo (no signup) or self-host it free from GitHub — see the next post for a step-by-step Docker guide.